Wednesday, April 28, 2004

Is Sea Level Rising?
Yesterday's blog was about a movie portraying climate change happening in weeks. Of course that scenario is a wild exaggeration, beyond even the most hysterical of expert's claims. An article from this week's Economist looks in the other direction, citing a fascinating study of water wells in Israel over the last 2000 years. The conclusion is that, at least in the Mediterranean, sea level has been very stable until the last century or so, and then rising since, coinciding with the runup in atmospheric carbon dioxide associated with industrialization.

I won't argue that this is anything more than another data point in a very complex picture. And I don't want to beat the climate horse to death, since I have devoted a fair amount of space in my blog to this topic. However, it occurred to me that I've never stated why I think this issue is important and worth doing something about. It's time I remedied that.

The view of climate change that most of us get from the popular media has the world warming gradually, by a few degrees Celsius over the next century. If that were all there was to it, I would resign myself to needing a few more Hawaiian shirts. Even the concerns about how this could alter regional and local weather patterns and expand the ranges of infectious diseases are all within the realm of things we could cope with, at some cost. (Clearly these effects would cause greater hardships in developing countries, and I don't mean to be callous about it.)

In a gradually warming world, adaptation is a perfectly reasonable strategy. After all, the planet was warmer than it is now several times in the past, without life vanishing. What has me worried, though, is a much more dangerous possible path of climate change.

To a large degree, the earth's climate is self-correcting. If you shine more sunlight on it, extra water evaporates, some of that drops out as snow at the poles, which expand and get whiter, reflecting more sunlight, and we come back into some kind of balance. (Any physicists or climatologists out there are cringing at this simplistic view of the mechanisms involved.)

Anyway, all of this functions like a sort of buffer. But like the chemical buffer systems you might have played with in your high school chemistry class, that allowed you to add acid or base without changing the overall acidity of the solution very much, this effect only works over some range. You can overwhelm it, at which point you no longer get nice, gradual changes. And that in a nutshell is what worries me about climate change: after some unknown--and possibly unknowable in advance--amount of warming, we might move out of the smooth buffering zone and into a zone of unpredictable, non-linear responses.

There has been a fair amount of talk about disruptions of the North Atlantic current as a possible mechanism for sudden and unpredictable climate change. This is one example of how a non-linear response to climate change could happen. If it occurred, it would be bigger than any natural disaster or combination of disasters that we have dealt with since the dawn of civilization. It has the potential to change our world faster and more dramatically than our ability to adapt could handle. The implications for governments and businesses would be profound.

Abrupt, non-linear climate change would therefore be very bad, but no one can predict whether or when it will happen. I see this situation as very similar to the question of whether I should insure my home against fire. I know it's highly unlikely, and I can look at statistical averages to estimate how much I should pay for insurance. But for the individual, statistically-derived expected values aren't very useful. If it happens and I'm not insured, it will affect my family in ways that are unacceptable.

In my mind, the Kyoto Treaty and similar measures, which would clearly impose costs on our economy, act as an insurance policy against something we simply can't afford to deal with, were it to occur. Even if all we can do is delay it or keep the change in the range of gradual shifts, that would be worth a lot. And if it never happens, well, we've paid for an insurance policy that we are happy not to have to collect on.

No comments: